Rare earth magnet and method for manufacturing the same

Abstract

Provided is a rare earth magnet and a method for manufacturing the same, which achieve both high magnetic properties and low eddy current loss. The rare earth magnet comprises coated granulated magnet powder particles, each of which comprises a granulated magnet powder particle and a coating of an insulating material on a surface thereof, the granulated magnet powder particle including a plurality of flake-shaped rare earth magnet powder particles bound in layers. The method of manufacturing the rare earth magnet comprises performing a granulating operation which includes binding flake-shaped rare earth magnet powder particles in layers to produce granulated magnet powder particles, and performing a coating operation which includes adding an insulating material to the granulated magnet powder particles to produce coated granulated magnet powder particles 5, each having a coating 4 thereon.

1 . A rare earth magnet comprising coated granulated magnet powder particles, each of which comprises a granulated magnet powder particle and a coating of an insulating material on a surface thereof, the granulated magnet powder particle including a plurality of flake-shaped rare earth magnet powder particles bound in layers and stacked in a stacking direction. 
     
     
         2 . The rare earth magnet as claimed in  claim 1 , wherein the granulated magnet powder particle has a thickness of 40 μm to 300 μm in the stacking direction. 
     
     
         3 . The rare earth magnet as claimed in  claim 1 , wherein the granulated magnet powder particle has a thickness in the stacking direction that is smaller than particle sizes of the rare earth magnet powder particles thereof. 
     
     
         4 . A method for manufacturing a rare earth magnet comprising:
 binding a plurality of flake-shaped rare earth magnet powder particles in layers to produce granulated magnet powder particles, each of which is formed by a plurality of the flake-shaped rare earth magnet powder particles stacked in a stacking direction;   adding an insulating material to the granulated magnet powder particles to produce coated granulated magnet powder particles, such that each of the coated granulated magnet powder particles comprises the flake-shaped rare earth magnet powder particles and a coating of the insulating material on a surface thereof; and   performing a compression molding operation, the compression molding operation comprising placing the coated granulated magnet powder particles in a mold configured to allow for pressurization and compressively deforming the coated granulated magnet powder particles with the mold, thereby producing the rare earth magnet.   
     
     
         5 . The method as claimed in  claim 4 , wherein the step of adding the insulating material comprises spraying a first dispersion solution containing a binding agent, the binding agent including a substance that decomposes at a temperature below a heat input temperature during the compression molding operation without leaving any residue, to the flake-shaped rare earth magnet powder particles that are caused to be tumbling and flowing, thereby binding the flake-shaped rare earth magnet powder particles in layers. 
     
     
         6 . The method as claimed in  claim 4 , wherein the step of adding the insulating material comprises spraying a second dispersion solution containing the insulating material and a binding agent to add the insulating material to the flake-shaped rare earth magnet powder particle, thereby producing the coated granulated magnet powder particles. 
     
     
         7 . The method as claimed in  claim 4 , wherein the step of performing the compression molding operation comprises:
 performing a first molding operation which includes placing the coated granulated magnet powder particles in the mold configured to allow for pressurization in a first direction, and applying pressure to the coated granulated magnet powder particles in the mold in the first direction to produce a first molded product; and   performing a second molding operation which includes applying pressure to the first molded product in second direction that intersects with the first direction, thereby plastically deforming the first molded product to produce the rare earth magnet.